Some toothbrushes are provided with functions for estimating a brushing area by calculating trajectories through the use of accelerometers, gyroscopes, or the like.
For example, JP-2009-240760A (Patent Citation 1) and JP-2009-240759A (Patent Citation 2) disclose estimating a brushing area using an accelerometer. These patent citations furthermore disclose using a camera, a temperature sensor, or a distance sensor to determine whether a surface is, for example, the buccal-side surface of the lower-left jaw or the lingual-side surface of the lower-right jaw.